The invention concerns a pump arrangement, in particular a centrifugal pump, in particular a main coolant pump for power stations, a protective valve and the use of a protective valve in a pump arrangement.
Such pumps have multi-stage hydrodynamic sealing systems with a so-called controlled leakage. These axial face sealing systems allow a defined pressure division between the stages of the axial face sealing system, and the dissipation of the heat yield from the individual steps which amounts to several kilowatts. In normal operation, the controlled leakage is fed from a sealing water system which thus ensures a seal against the system and prevents the hot delivery medium from entering the seal housing. To protect the sealing part from high temperatures and shocks, it must be ensured that if no sealing water is available, either the inflowing hot water is cooled or the pump is shut down and the leakage valve closed.
The object of the invention is to create a device which, on failure of the sealing water supply, ensures an independent blocking of the controlled leakage and can maintain this block during further operation.
The object of the invention is achieved by a pump arrangement with a pump housing which defines an interior with an inlet opening for aspirating a delivery medium and an outlet opening for expelling the delivery medium, and which also defines a chamber connected to the interior, a sealing water system comprising a first conduit system for supplying sealing water to the chamber defined by the pump housing, a second conduit system for evacuating a controlled leakage flow from the chamber defined by the pump housing, and a protective valve arranged in the second conduit system for blocking the leakage flow evacuated from the chamber.
In a preferred implementation of the pump arrangement, the chamber is a multi-stage hydrodynamic sealing system which securely seals the chamber.
In a particular embodiment, the sealing system comprises a plurality of spring-mounted axial face seals.
The security of the sealing system is further increased if the sealing system comprises a pressure-controlled seal which is open in operation, in particular a nitrogen seal, water seal or similar.
A particularly good operating method is achieved if medium is extracted from the leakage flow via a conduit and supplied to a pressure chamber in the seal arranged inside the chamber.
Since the leakage protection valve, once closed, is not able to open by itself as long as a positive pressure predominates in front of the protection valve, a shut-off fitting is connected in parallel to the protective valve.
The object of the invention is furthermore achieved by a protective valve with a valve housing part, a valve chamber formed in the valve housing part, a valve housing cover which is arranged on the valve housing part and comprises a passage bore communicating with the valve chamber, a valve seat provided on the housing cover, a valve tappet provided with a valve cone and a rest device, a spring device supported on the valve housing cover and lying on the rest device, and with thermosensitive actuators which expand on heating arranged on the side of the rest device opposite the spring device.
According to the invention, the actuators are made from a form-memory alloy or comprise a bimetal arrangement. This offers many design possibilities for the actuators.
The actuators may be configured as a ring or sleeve, of one or more pieces, and/or as a cup spring, whereby these can be optimally adapted to the conditions in the valve chamber.
In an advantageous refinement of the invention, the valve housing part has a housing portion with reduced inner diameter which serves as a support shoulder for the actuators.
According to the invention, an axial groove is formed on the inner periphery of the housing portion facing the valve tappet, and an axial groove oriented parallel to the axial groove is formed on the valve tappet, wherein an adjustment spring is inserted in said grooves. The resulting twist prevention serves to ensure that the valve cone and valve seat always meet at the same point and that the actuators are not distorted.
The object of the invention is furthermore achieved by the use of such a protective valve in a pump arrangement.
Exemplary embodiments of the invention are shown in the drawings and described in more detail below. These show: